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Discussion Starter · #1 ·
Hey folks. Anyone know what the break-in period is for hollowtech II bottom bracket bearings? I've done the search, and haven't found the info I'm looking for.

After the install, where I followed manufacturer recommended torque for the preload, I feel like I'm working quite a bit harder than I did with my old square taper bottom bracket. Could be extra beer from the night before - more likely the bearings. What sort of time period or mileage am I looking at till these things are a little smoother? It should be worth noting that they felt a touch tight when playing with them prior to install, so I'm inclined to believe that there is a break in period.
 

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Bearings don't really break in, but the seals will loosen up after a bit of riding and external BBs usually do have more seal drag

That said, if there are tight enough that you can actually feel a difference while riding then you must have the preload bolt too tight. Too much preload will make the bearings bind and make them feel slow
 

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External BB? If you compare the spin resistance between external bb and square by cranking with you hand (free spin) then you may ge nervous as external bb feels a lot more drag by design. On the bike, I doubt it makes any difference though. My 3 year old XTR (970) spins freely about 2 rotations where my square taper XT goes weeeeee... I take off all grease when I clean, and the bearings spin freely. Pack grease, put the seals on, it gets tighter. Then put them in the cups, it gets even tighter. So yea it's by design, I would try not to think about it - then you'll forget it by next week.
 

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Unless you WAY overtightened things there's no way there's enough extra drag for you to notice. Either

a) You have way too much preload on the bearings or
b) Placebo effect
 

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Discussion Starter · #6 ·
You fellas were right - preload was too high. Went for a spin today after loosening things up and found that once again, I am the super-human spinning machine I once was.

Thanks all.
 
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